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At least 109 records · Page 6Linked to original sources

Interlimb coordination following stroke.

Studies investigating whether simultaneous bilateral movements can facilitate performance of the impaired limb(s) of stroke patients have returned mixed results. In the present study we compared unilateral limb performance (amplitude, cycle duration) with performance during an interlimb coordination task involving both homologous (both arms, both legs) and non-homologous (one arm, one leg) limbs in stroke participants (n=7) and healthy age-matched controls (n=7). In addition, the effect of on-line augmented visual feedback on interlimb coordination was investigated. Participants performed cyclical flexion-extension movements of the arms and legs in the sagittal plane paced by an auditory metronome (1 Hz). Movement amplitudes were larger and cycle durations shorter during homologous limb coordination than non-homologous coordination. Compared with unilateral movements both groups had reduced movement amplitudes and the stroke group increased cycle duration when interlimb coordination tasks were performed. These effects were most evident during non-homologous (arm and leg) coordination. No evidence of facilitation of the impaired limb(s) was found in any of the interlimb coordination conditions. Augmented visual feedback had minimal effect on the movements of control participants but lead to an increase of cycle duration for stroke participants.

Adult↗

Interactive fitting augmented by force-feedback and virtual reality.

The synthesis of low-resolution electron microscopy data with high-resolution molecular structures has become a common routine in the modeling of biomolecular assemblies. In contrast to algorithmic "black box" solutions, the interactive "fitting by eye" takes advantage of an expert's structural or biochemical knowledge and can be used with very noisy experimental data. In the solution proposed in this paper, we support the expert user in an interactive fitting session by haptic rendering and virtual reality. The quantitative and tactile feedback facilitates and objectifies the otherwise unrestrained modeling. We introduce a highly accurate reduced representation of the gradient of the cross-correlation coefficient that sustains force updates for haptic rendering at sufficiently high refresh rates.

Algorithms↗

A do-it-yourself membrane-activated auditory feedback device for weight bearing and gait training: a case report.

An augmented auditory feedback device comprised of a thin membrane switch mini-buzzer, and battery is described as a modification of a previously described feedback device. The membrane switch can be customized for the patient and is designed to fit inside a patient's shoe without altering the heel height. Its appeal lies in its simplicity of construction, low cost, and ease of implementation during a patient's training for weight bearing and gait. An ever-present source of information, it provides performance-relevant cues to both patient and clinician about the occurrence, duration, and location of a force component of motor performance. The report includes suggested applications of the device, instructions to construct it, and a case report in which the device was used to improve weight bearing and gait in a cognitively healthy person with spina bifida.

Biofeedback, Psychology↗

Superoxide enhances tubuloglomerular feedback by constricting the afferent arteriole.

BACKGROUND: Superoxide (O(2) (-)) has been shown to augment tubuloglomerular feedback (TGF) both in vivo and in vitro by scavenging nitric oxide (NO) in the macula densa (MD). We hypothesized that in addition to this mechanism O(2) (-) potentiates TGF by acting directly on the afferent arteriole (Af-Art). METHODS: Microdissected Af-Arts and adherent tubular segments containing the MD were simultaneously microperfused in vitro, maintaining Af-Art pressure at 60 mm Hg. TGF response was determined by measuring changes in Af-Art diameter while increasing NaCl in the MD perfusate from 11/10 to 81/80 mmol/L Na/Cl. RESULTS: To determine whether O(2) (-) acts at the MD in the absence of MD NO, we inhibited MD nNOS with 7-nitroindazole (7-NI) and added Tempol to the lumen. When 7-NI was added to the MD lumen, it increased TGF from 2.3 +/- 0.2 to 4.2 +/- 0.2 microm (P < 0.01). When Tempol was added to the MD lumen in the presence of 7-NI, it had no effect on TGF. To investigate whether O(2) (-) has any effect via the Af-Art in the absence of MD NO, we inhibited MD nNOS with 7-NI and added Tempol to the bath to scavenge O(2) (-) in the Af-Art. Adding Tempol to the bath with 7-NI in the MD lumen reduced TGF from 3.9 +/- 0.3 to 2.8 +/- 0.5 microm (P < 0.05 vs. 7-NI). To see if this effect was due to O(2) (-) scavenging NO production by the endothelium, we repeated the experiment in Af-Arts with damaged endothelium and found that adding Tempol to the bath lowered TGF from 3.4 +/- 0.9 to 1.2 +/- 0.6 microm (P < 0.01). When catalase was added to the bath together with Tempol, TGF response was not modified. CONCLUSION: We concluded that it is O(2) (-) rather than H(2)O(2) that enhances TGF response, both directly by constricting the Af-Art and indirectly by scavenging NO in the MD.

Animals↗

Effect of multisource feedback on resident communication skills and professionalism: a randomized controlled trial.

OBJECTIVE: To determine whether augmenting standard feedback on resident performance with a multisource feedback intervention improved pediatric resident communication skills and professionalism. DESIGN: Randomized controlled trial. SETTING: Children's Hospital Medical Center, Cincinnati, Ohio, from June 21, 2004, to July 7, 2005. PARTICIPANTS: Thirty-six first-year pediatric residents. INTERVENTIONS: Residents assigned to the multisource feedback group (n = 18) completed a self-assessment, received a feedback report about baseline parent and nurse evaluations, and participated in a tailored coaching session in addition to receiving standard feedback. Residents in the control group (n = 18) received standard feedback only. The control group and their residency directors were blinded to parent and nurse evaluations until the end of the study. MAIN OUTCOME MEASURES: Residents' specific communication skills and professional behaviors were rated by parents and nurses of pediatric patients. Both groups were evaluated at baseline and after 5 months. Scores were calculated on each item as percentage in the highest response category. RESULTS: Both groups had comparable baseline characteristics and ratings. Parent ratings increased for both groups. While parent ratings increased more for the multisource feedback group, differences between groups were not statistically significant. In contrast, nurse ratings increased for the multisource feedback group and decreased for the control group. The difference in change between groups was statistically significant for communicating effectively with the patient and family (35%; 95% confidence interval, 11.0%-58.0%), timeliness of completing tasks (30%; 95% confidence interval, 7.9%-53.0%), and demonstrating responsibility and accountability (26%; 95% confidence interval, 2.9%-49.0%). CONCLUSION: A multisource feedback intervention positively affected communication skills and professional behavior among pediatric residents.

Adult↗

Personality correlates of bidirectional heart-rate control.

This study examined the combined effects of personality with instruction and treatment variables in human operant heart-rate conditioning. The Edwards Personal Preference Schedule was administered to 50 subjects tested for bidirectional heart-rate control during no-feedback and analogue auditory feedback conditions. Findings indicated that relative to pre-trial baselines, subjects were able significantly to alter heart rates according to instructed direction of change, but treatment effects for augmented sensory feedback were not reliable. Correlational analyses employing personality variables demonstrated that different traits define successful speeding and reduction performance. Further, post hoc analyses for personality high-low classification X treatment X instructions effects indicated that personality variables of succorance and abasement moderated treatment effects for heart-rate reduction. Questions are raised concerning the efficacy of proportional auditory treatment in biofeedback training.

Adult↗

The luteinizing hormone response to luteinizing hormone-releasing hormone, prostaglandin E2 and naloxone is modulated by divergent sensitivity to testosterone feedback.

Testosterone (T) levels necessary to suppress LH secretion are reduced in starvation, and increased feedback sensitivity to T is therefore postulated. The luteinizing hormone (LH) response to naloxone (Nal) is more easily suppressed by starvation than is its response to prostaglandin E2 (PGE2) and to luteinizing hormone-releasing hormone (LRH). If the divergent suppressibility is due to altered feedback sensitivity in starvation, it should be feasible to reproduce this phenomenon in normally nourished rats by increasing T levels. Adult male Wistar rats were castrated and implanted with silicone capsules (0-2.6 cm) filled with T. Indwelling jugular cannulae were implanted. On days 4 to 8 post operation rats were injected iv with LRH (25-400 ng/kg body weight), PGE2 (0.05-1.0 mg/kg body weight) or Nal (0.5-50 mg/kg body weight). Blood samples were drawn before and 10, 20 and 30 min after injection. Results show that the response to Nal was already suppressed at medium T levels. The LH response to PGE2 was diminished to a greater extent than the response to LRH but was never completely suppressed by increasing steroid levels. These data are compatible with the hypothesis that steroid feedback sensitivity augments with increasing levels of regulation of the hypothalamic-pituitary-gonadal axis.

Animals↗

Enhanced tubuloglomerular feedback in Cyp1a1-Ren2 transgenic rats with inducible ANG II-dependent malignant hypertension.

The present study was performed to evaluate tubuloglomerular feedback responses in transgenic rats [TGR(Cypa1a1Ren2)] with inducible malignant hypertension and to determine the degree to which feedback responsiveness is modulated by ANG II in these rats. Male Cyp1a1-Ren2 rats were fed a normal diet containing the aryl hydrocarbon indole-3-carbinol (I3C; 0.3%), for 5-6 days to stimulate expression of the Cyp1a1-Ren2 transgene and, thereby, to induce malignant hypertension. Stop-flow pressure (SFP) feedback responses to a late proximal perfusion rate of 40 nl/min were assessed in pentobarbital sodium-anesthetized rats during control conditions and after administration of the AT(1) receptor antagonist candesartan (0.1 mg/kg iv). Rats induced with I3C (n = 6) exhibited elevated mean arterial pressure and increased maximal SFP feedback responses compared with noninduced rats (n = 4; 163 +/- 4 vs. 130 +/- 2 mmHg, P < 0.01 and 16.3 +/- 1.4 vs. 11.7 +/- 0.5 mmHg, P < 0.05, respectively). Systemic candesartan decreased arterial pressure (to 98 +/- 7 and to 101 +/- 5 mmHg, respectively, P < 0.001) and attenuated SFP feedback responses (to 2.0 +/- 0.4 and to 3.3 +/- 0.9 mmHg, respectively, P < 0.01) in both hypertensive and normotensive rats. In additional experiments, peritubular capillary infusion of 10(-3) M candesartan did not alter arterial pressure but attenuated feedback responses in both hypertensive (19.3 +/- 1.4 to 8.8 +/- 0.9 mmHg, P < 0.01, n = 9) and normotensive Cyp1a1-Ren2 rats (9.0 +/- 0.8 to 4.7 +/- 0.6 mmHg, P < 0.01, n = 7). The present findings indicate that Cyp1a1-Ren2 rats with ANG II-dependent malignant hypertension exhibit augmented tubuloglomerular feedback responses. The data also show that AT(1) receptor activation by ANG II contributes to the enhanced feedback responsiveness in Cyp1a1-Ren2 rats with malignant hypertension.

Angiotensin II↗

The effect of a simulated knee joint effusion on postural control in healthy subjects.

OBJECTIVE: To determine the effects of a simulated knee joint effusion on center of pressure (COP) path and mean power frequency (MPF) during standing. DESIGN: Quasi-experimental design. SETTING: Sports injury research laboratory in a university setting. PARTICIPANTS: Twenty healthy volunteers, 10 of whom (age, 20.1+/-2.4y; height, 168.0+/-8.1cm; weight, 70.4+/-13.3kg) were assigned to an effusion group and 10 of whom (age, 25+/-3.8y; height, 169.4+/-8.9cm; weight, 74.7+/-7.7kg) were assigned to a control group. INTERVENTIONS: COP data were collected before and after a 60-mL injection of sterile saline into the knee joint space. MAIN OUTCOME MEASURES: COP path and mediolateral and anteroposterior MPF. RESULTS: COP path decreased after the effusion (pre-effusion mean, 92.2+/-21.9cm; posteffusion mean, 77.27+/-23.0cm). No change was found within the control group for COP path (P>.05). No differences were detected before or after joint effusion when the MPF was examined (P>.05). CONCLUSIONS: Possible explanations for the improved postural control after the effusion include additional somatosensory feedback, an augmented neural drive to the soleus, and/or increased capsular tension.

Adult↗

Calcium-dependent immediate feedback control of inositol 1,4,5-triphosphate-induced Ca2+ release.

The temporal and spatial distribution of increases in intracellular Ca2+ concentration is an important factor in cellular signal transduction. Inositol 1,4,5-trisphosphate (InsP3) plays a key part in agonist-induced Ca2+ release, which can take place abruptly and in a confined space by a mechanism that is not fully understood. Here we analyse the kinetics of InsP3-induced Ca2+ release following flash photolysis of caged InsP3 or caged Ca2+, and demonstrate that Ca(2+)-dependent immediate feedback control is an important determinant of the time course of Ca2+ release. The positive feedback mechanism is also important for the 'loading dependence' of InsP3-induced Ca2+ release. Furthermore, our results support the operation of positive cooperativity in channel opening and feedback control augments the steep InsP3 concentration-Ca2+ release relation. These inherent properties of InsP3-induced Ca2+ release are expected to give rise to temporally abrupt and/or spatially confined Ca2+ release within the cell.

Animals↗

Auditory concurrent feedback benefits on the circle performed in gymnastics.

In this study, we examined the effectiveness of auditory concurrent feedback on body segmental alignment during the circle movement performed on a pommel horse. Eighteen gymnasts were assigned to one of two groups: a concurrent auditory feedback group (experimental) or a control group that received no concurrent feedback. After 2 weeks of training (300 circles), the body segmental alignment (BSA) of the experimental group had improved by 2.3% between the pre test (85.7 +/- 4.8% BSA(max)) and the post test (87.7 +/- 4.0% BSA(max)). Furthermore, the results of a retention test administered 2 weeks after the post test revealed no decline in performance for the experimental group. No gains in body segmental alignment were found for the control group. It was concluded that augmented auditory feedback made available in real time can be used to correct complex movements, such as the circle movement on a pommel horse, and does not appear to lead to information-dependence despite the frequent administration of feedback. The auditory signal available in real time could help gymnasts to become more objective about their own intrinsic information necessary for the refinement of the circle movement.

Adolescent↗

A comparison of the mechanisms and some properties of instructed sudomotor and cardiac control.

Instructed control defined as differential compliance with verbal instructions to increase and decrease a response was assessed when a change in sudomotor activation or heart rate was specified as the behavioral goal. Instructed control of heart rate was evident prior to explicit feedback training for this response, but instructed control of sudomotor activation defined as finger sweating and measured as skin conductance was not. Feedback training subsequently established instructed control of sudomotor responding, but such training did not lead to a significant improvement in control of heart rate. Explicit strategy suggestions emphasizing emotional responding and intended or actual movement appeared to interfere with the performance of instructed control under both target conditions. Instructed changes in heart rate were attended by correlated changes in somatomotor and respiratory function. Somatomotor and respiratory responses were also observed when subjects were instructed to change sudomotor activation, but these correlated activities were of small magnitude and were not augmented by feedback training as was target responding. Several accounts of the basis for differences that were evident between the target conditions with respect to feedback effects and response patterns are discussed.

Adult↗

Single nephron comparison of the effect of loop of Henle flow on filtration rate and pressure in control and angiotensin II-infused rats.

Experiments were performed in control and angiotensin II-infused rats to test whether the tubuloglomerular feedback responses of early proximal flow rate (VEP) and stop flow pressure (PSF) are elicited by the same flow rate changes. Paired measurements in the same nephron revealed that VEP responses were shifted to the left compared to those of PSF. The flow rate at which the response was half maximum, V1/2, was 14.7 +/- 1.25 nl/min for VEP and 18.9 +/- 0.97 nl/min for PSF (p less than 0.05). This difference in flow dependency was abolished by angiotensin II infusion (V1/2 was 14.6 +/- 0.87 nl/min for VEP and 15.4 +/- 1.09 nl/min for PSF). Furthermore, angiotensin infusion markedly augmented the feedback response magnitude.

Angiotensin II↗

Effect of step-synchronized vibration stimulation of soles on gait in Parkinson's disease: a pilot study.

BACKGROUND: Previous studies have suggested that impaired proprioceptive processing in the striatum may contribute to abnormal gait in Parkinson's disease (PD). METHODS: This pilot study assessed the effects of enhanced proprioceptive feedback using step-synchronized vibration stimulation of the soles (S-VS) on gait in PD. S-VS was used in 8 PD subjects (3 women and 5 men, age range 44-79 years, on medication) and 8 age-matched healthy subjects (5 women and 3 men). PD subjects had mild or moderate gait impairment associated with abnormal balance, but they did not have gait freezing. Three vibratory devices (VDs) were embedded in elastic insoles (one below the heel and two below the forefoot areas) inserted into the shoes. Each VD operates independently and has a pressure switch that activates the underlying vibratory actuator. The VD delivered the 70-Hz suprathreshold vibration pulse upon touch by the heel or forefoot, and the vibration pulse was deactivated upon respective push-offs. Six-minute hallway walking was studied with and without S-VS. Gait characteristics were measured using the force-sensitive foot switches. The primary outcome was the stride variability expressed as a coefficient of variation (CV), a measure of gait steadiness. Secondary outcome measures were walking distance and speed, stride length and duration, cadence, stance, swing and double support duration, and respective CVs (if applicable). RESULTS: The walking speed (p < 0.04) and the CV of the stride interval (p < 0.02) differed between the groups and S-VS conditions. In the PD group, S-VS decreased stride variability (p < 0.002), increased walking speed (p < 0.0001), stride duration (p < 0.01), stride length (p < 0.0002), and cadence (p < 0.03). In the control group, S-VS decreased stride variability (p < 0.006) and increased gait speed (p < 0.03), but other locomotion parameters were not significantly altered. CONCLUSION: Augmented sensory feedback improves parkinsonian gait steadiness in the short-term setting. Because the suprathreshold stimulation prevented blinding of subjects, the learning effect and increased attention can be a confounding factor underlying results. Long-term studies are needed to establish the clinical value of the S-VS.

Journal Article↗

Recruitment for the Coronary Primary Prevention Trial.

A preliminary account of some aspects of recruitment for the Coronary Primary Prevention Trial is provided. Extension of recruitment sources to include various forms of community screening resulted in more rapid acquisition of potential participants than was possible when recruitment was restricted to the more traditional sources of physician and laboratory referral. Extended recruitment was supported by augmented data feedback and by the development of the job of recruitment coordinator at each participating clinic. The identification of delays in reaching the maximal recruitment rate from particular sources points to the need for detailed planning of a recruitment campaign before large-scale clinical trials are begun.

Clinical Trials as Topic↗

Governing coordination: behavioural principles and neural correlates.

The coordination of movement is governed by a coalition of constraints. The expression of these constraints ranges from the concrete--the restricted range of motion offered by the mechanical configuration of our muscles and joints; to the abstract--the difficulty that we experience in combining simple movements into complex rhythms. We seek to illustrate that the various constraints on coordination are complementary and inclusive, and the means by which their expression and interaction are mediated systematically by the integrative action of the central nervous system (CNS). Beyond identifying the general principles at the behavioural level that govern the mutual interplay of constraints, we attempt to demonstrate that these principles have as their foundation specific functional properties of the cortical motor systems. We propose that regions of the brain upstream of the motor cortex may play a significant role in mediating interactions between the functional representations of muscles engaged in sensorimotor coordination tasks. We also argue that activity in these "supramotor" regions may mediate the stabilising role of augmented sensory feedback.

Animals↗

Neurophysiological analysis of long-term potentiation in mammalian brain.

Long-term potentiation (LTP) is a persistent increase in postsynaptic response following a high-frequency presynaptic activation. Characteristic LTP features, including input specificity and associativity, make it a popular model to study memory mechanisms. Mechanisms of LTP induction and maintenance are briefly reviewed. Increased intracellular Ca2+ concentration is shown to be critical for LTP induction. This increase is believed to be based on Ca2+ influx secondary to activation of N-methyl-D-aspartate (NMDA) subtype of glutamate receptors. Existence of other sources of Ca2+ increase and other critical factors is now becoming evident. They include voltage-dependent Ca2+ channels, Ca2+ intracellular stores, metabotropic glutamate receptors, 'modulatory' transmitters. An example of an involvement of voltage-dependent Ca2+ channels is potentiation induced by intracellular depolarizing pulses. LTP can be divided into decremental earlier (E-LTP) and non-decremental late (L-LTP) phases which explains some inconsistencies in studies of LTP mechanisms. E-LTP is suggested to be based on a transient increase in presynaptic release probabilities. A hypothesis is considered which explains L-LTP by suggesting that Ca2+ activates structural changes leading to an increase in the synaptic gap resistance. This enhances positive synaptic electrical feedback and augments release probability. The hypothesis predicts specific morphological changes, synchronous transmitter release of two or several quanta in some central synapses and the amplification of such synchronization following LTP induction. Data are discussed which maintain these predictions.

Animals↗